Madison, Wisconsin - A new University of Wisconsin-Madison analysis uncovered a startling fact: Women’s mortality rates in almost 43 percent of American counties actually got worse during the 15 years ending in 2006.

In other words, while mortality rates improved in most U.S. counties, women in some parts of America, especially those in the West and South, faced worse premature mortality rates (dying at or before age 75, which is considered by epidemiologists to mark premature death).

The maps below show the differences in male and female mortality (maps courtesy of Health Affairs).

Change In Female Mortality Rates from 1992-96 to 2002-06

Of the 3,140 counties in the sample, 603 (19.2 percent) experienced substantial improvement (a reduction of 6.6 percent to 40.7 percent) in female mortality rates, and 1,193 counties (38 percent of the sample) experienced minimal improvement (a reduction of less than 1 percent to 6.5 percent). The 28 counties that experienced no change in female mortality rates were grouped with with the 1,316 counties that experienced worsening female mortality rates (an increase of less than 1 percent to 37.3 percent). View a larger version

Change In Male Mortality Rates from 1992-96 to 2002-06

Of the 3,140 counties in the sample, 1,012 (32.3 percent) experienced substantial improvement (a reduction of 11.7 percent to 61.4 percent) in male mortality rates, and 2,020 counties (64.3 percent of the sample) experienced minimal improvement (a reduction of less than 1 percent to 11.6 percent). The three counties that experienced no change in male mortality rates were grouped with the 105 counties that experienced worsening male mortality rates (any increase). View a larger version

“We decided to look at the change in health outcomes over time, and were actually shocked to see that female mortality rates were worsening in more than 42 percent of counties,” says Dr. David Kindig, professor emeritus of population health sciences at the University of Wisconsin School of Medicine and Public Health (UW SMPH).

A mortality rate is a ratio of the number of deaths in a group compared with the total population of the group. The trend showed that female mortality rates rose in 42.8 percent of counties while male mortality rose in 3.4 percent of counties over the same time period.

Higher female mortality was most strongly associated with living in the rural South or the West, higher smoking rates, and lower education rates. The study found that access to primary care physicians did not affect changes in mortality rates.

To do the study, Kindig and his collaborator Erika R. Cheng, a doctoral candidate at the UW School of Medicine and Public Health, averaged the mortality rates over five years (1992-1996) at the beginning of the study and five years (2002-2006) at the end, and compared the two averages. They also used a statistical “smoothing” method to make sure that changes in small numbers from lightly populated counties did not skew the results.

“Socioeconomic and behavioral factors are underappreciated for their effects on health, but with data like this, we see that those factors are important again and again,” says Kindig, who was recently named to lead an Institute of Medicine roundtable to learn why Americans have worse health and shorter lives than people in other rich, industrialized nations despite spending more on medical care than any other nation.

“Our results underscore the complicated policy reality that there is no single silver bullet for population health improvement,” the authors concluded. “Investments in all determinants of health – including health care, public health, health behaviors and residents’ social and physical environments – will be required.”